On Tue, Apr 05, 2016 at 12:12:29PM +0800, Yuyang Du wrote: > Currently, load_avg = scale_load_down(load) * runnable%. The extra scaling > down of load does not make much sense, because load_avg is primarily THE > load and on top of that, we take runnable time into account. > > We therefore remove scale_load_down() for load_avg. But we need to > carefully consider the overflow risk if load has higher range > (2*SCHED_FIXEDPOINT_SHIFT). The only case an overflow may occur due > to us is on 64bit kernel with increased load range. In that case, > the 64bit load_sum can afford 4251057 (=2^64/47742/88761/1024) > entities with the highest load (=88761*1024) always runnable on one > single cfs_rq, which may be an issue, but should be fine. Even if this > occurs at the end of day, on the condition where it occurs, the > load average will not be useful anyway.
I do feel we need a little more words on the actual ramification of overflowing here. Yes, having 4m tasks on a single runqueue will be somewhat unlikely, but if it happens, then what will the user experience? How long (if ever) does it take for numbers to correct themselves etc.. > Signed-off-by: Yuyang Du <[email protected]> > [update calculate_imbalance] > Signed-off-by: Vincent Guittot <[email protected]> This SoB Chain suggests you wrote it and Vincent send it on, yet this email is from you and Vincent isn't anywhere. Something's not right.
